[libc++] Disable cv-qualified arithmetic hash specializations #155786

philnik777 · 2025-08-28T08:38:11Z

#140407 accidentally enabled hash for cv-qualified types. This patch disables these specializations again.

llvmbot · 2025-08-28T08:38:47Z

@llvm/pr-subscribers-libcxx

Author: Nikolas Klauser (philnik777)

Changes

#140407 accidentally enabled hash for cv-qualified types. This patch disables these specializations again.

Full diff: https://github.com/llvm/llvm-project/pull/155786.diff

7 Files Affected:

(modified) libcxx/include/CMakeLists.txt (+1)
(modified) libcxx/include/__functional/hash.h (+10-4)
(added) libcxx/include/__type_traits/is_unqualified.h (+25)
(modified) libcxx/include/module.modulemap.in (+1)
(modified) libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp (+5)
(modified) libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp (+5)
(modified) libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp (+5)

diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
index 6fd16419f0c49..1f91b4828d4d3 100644
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -872,6 +872,7 @@ set(files
   __type_traits/is_trivially_relocatable.h
   __type_traits/is_unbounded_array.h
   __type_traits/is_union.h
+  __type_traits/is_unqualified.h
   __type_traits/is_unsigned.h
   __type_traits/is_valid_expansion.h
   __type_traits/is_void.h
diff --git a/libcxx/include/__functional/hash.h b/libcxx/include/__functional/hash.h
index 489a6f00b8a3d..d95b2c0884984 100644
--- a/libcxx/include/__functional/hash.h
+++ b/libcxx/include/__functional/hash.h
@@ -21,6 +21,7 @@
 #include <__type_traits/is_enum.h>
 #include <__type_traits/is_floating_point.h>
 #include <__type_traits/is_integral.h>
+#include <__type_traits/is_unqualified.h>
 #include <__type_traits/underlying_type.h>
 #include <__utility/pair.h>
 #include <__utility/swap.h>
@@ -355,7 +356,8 @@ struct __hash_impl {
 };
 
 template <class _Tp>
-struct __hash_impl<_Tp, __enable_if_t<is_enum<_Tp>::value> > : __unary_function<_Tp, size_t> {
+struct __hash_impl<_Tp, __enable_if_t<is_enum<_Tp>::value && __is_unqualified_v<_Tp>> >
+    : __unary_function<_Tp, size_t> {
   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
     using type = __underlying_type_t<_Tp>;
     return hash<type>()(static_cast<type>(__v));
@@ -363,17 +365,21 @@ struct __hash_impl<_Tp, __enable_if_t<is_enum<_Tp>::value> > : __unary_function<
 };
 
 template <class _Tp>
-struct __hash_impl<_Tp, __enable_if_t<is_integral<_Tp>::value && (sizeof(_Tp) <= sizeof(size_t))> >
+struct __hash_impl<
+    _Tp,
+    __enable_if_t<is_integral<_Tp>::value && __is_unqualified_v<_Tp> && (sizeof(_Tp) <= sizeof(size_t))> >
     : __unary_function<_Tp, size_t> {
   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT { return static_cast<size_t>(__v); }
 };
 
 template <class _Tp>
-struct __hash_impl<_Tp, __enable_if_t<is_integral<_Tp>::value && (sizeof(_Tp) > sizeof(size_t))> >
+struct __hash_impl<_Tp,
+                   __enable_if_t<is_integral<_Tp>::value && __is_unqualified_v<_Tp> && (sizeof(_Tp) > sizeof(size_t))> >
     : __scalar_hash<_Tp> {};
 
 template <class _Tp>
-struct __hash_impl<_Tp, __enable_if_t<is_floating_point<_Tp>::value> > : __scalar_hash<_Tp> {
+struct __hash_impl<_Tp, __enable_if_t<is_floating_point<_Tp>::value && __is_unqualified_v<_Tp> > >
+    : __scalar_hash<_Tp> {
   _LIBCPP_HIDE_FROM_ABI size_t operator()(_Tp __v) const _NOEXCEPT {
     // -0.0 and 0.0 should return same hash
     if (__v == 0.0f)
diff --git a/libcxx/include/__type_traits/is_unqualified.h b/libcxx/include/__type_traits/is_unqualified.h
new file mode 100644
index 0000000000000..7970b3611601f
--- /dev/null
+++ b/libcxx/include/__type_traits/is_unqualified.h
@@ -0,0 +1,25 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___TYPE_TRAITS_IS_UNQUALIFIED_H
+#define _LIBCPP___TYPE_TRAITS_IS_UNQUALIFIED_H
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp>
+inline const bool __is_unqualified_v = __is_same(_Tp, __remove_cvref(_Tp));
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___TYPE_TRAITS_IS_UNQUALIFIED_H
diff --git a/libcxx/include/module.modulemap.in b/libcxx/include/module.modulemap.in
index ee18d04c78d0e..c50c4dd73d4bb 100644
--- a/libcxx/include/module.modulemap.in
+++ b/libcxx/include/module.modulemap.in
@@ -335,6 +335,7 @@ module std_core [system] {
       header "__type_traits/is_union.h"
       export std_core.type_traits.integral_constant
     }
+    module is_unqualified { header "__type_traits/is_unqualified.h" }
     module is_unsigned {
       header "__type_traits/is_unsigned.h"
       export std_core.type_traits.integral_constant
diff --git a/libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp b/libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp
index fd1fbe5f113ba..b796960975ea1 100644
--- a/libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp
+++ b/libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp
@@ -19,6 +19,7 @@
 #include <limits>
 #include <type_traits>
 
+#include "poisoned_hash_helper.h"
 #include "test_macros.h"
 
 enum class Colors { red, orange, yellow, green, blue, indigo, violet };
@@ -33,6 +34,10 @@ template <class T>
 void
 test()
 {
+    test_hash_disabled<const T>();
+    test_hash_disabled<volatile T>();
+    test_hash_disabled<const volatile T>();
+
     typedef std::hash<T> H;
 #if TEST_STD_VER <= 17
     static_assert((std::is_same<typename H::argument_type, T>::value), "");
diff --git a/libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp b/libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp
index b8f85e193dc8f..bf3e38e619519 100644
--- a/libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp
+++ b/libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp
@@ -25,12 +25,17 @@
 #include <limits>
 #include <cmath>
 
+#include "poisoned_hash_helper.h"
 #include "test_macros.h"
 
 template <class T>
 void
 test()
 {
+    test_hash_disabled<const T>();
+    test_hash_disabled<volatile T>();
+    test_hash_disabled<const volatile T>();
+
     typedef std::hash<T> H;
 #if TEST_STD_VER <= 17
     static_assert((std::is_same<typename H::argument_type, T>::value), "");
diff --git a/libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp b/libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp
index 14af7093c1e36..cfa6b324ba323 100644
--- a/libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp
+++ b/libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp
@@ -24,12 +24,17 @@
 #include <limits>
 #include <type_traits>
 
+#include "poisoned_hash_helper.h"
 #include "test_macros.h"
 
 template <class T>
 void
 test()
 {
+    test_hash_disabled<const T>();
+    test_hash_disabled<volatile T>();
+    test_hash_disabled<const volatile T>();
+
     typedef std::hash<T> H;
 #if TEST_STD_VER <= 17
     static_assert((std::is_same<typename H::argument_type, T>::value), "");

github-actions · 2025-08-28T08:41:45Z

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff origin/main HEAD --extensions cpp,h -- libcxx/include/__type_traits/is_unqualified.h libcxx/include/__functional/hash.h libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp

⚠️
The reproduction instructions above might return results for more than one PR
in a stack if you are using a stacked PR workflow. You can limit the results by
changing origin/main to the base branch/commit you want to compare against.
⚠️

View the diff from clang-format here.

diff --git a/libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp b/libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp
index 05a19329f..e854bc363 100644
--- a/libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp
+++ b/libcxx/test/std/utilities/function.objects/unord.hash/enum.pass.cpp
@@ -38,12 +38,12 @@ void
 test()
 {
 #if TEST_STD_VER >= 11
-    test_hash_disabled<const T>();
-    test_hash_disabled<volatile T>();
-    test_hash_disabled<const volatile T>();
+  test_hash_disabled<const T>();
+  test_hash_disabled<volatile T>();
+  test_hash_disabled<const volatile T>();
 #endif
 
-    typedef std::hash<T> H;
+  typedef std::hash<T> H;
 #if TEST_STD_VER <= 17
     static_assert((std::is_same<typename H::argument_type, T>::value), "");
     static_assert((std::is_same<typename H::result_type, std::size_t>::value), "");
diff --git a/libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp b/libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp
index f6c31d068..b96fbbb68 100644
--- a/libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp
+++ b/libcxx/test/std/utilities/function.objects/unord.hash/floating.pass.cpp
@@ -36,12 +36,12 @@ void
 test()
 {
 #if TEST_STD_VER >= 11
-    test_hash_disabled<const T>();
-    test_hash_disabled<volatile T>();
-    test_hash_disabled<const volatile T>();
+  test_hash_disabled<const T>();
+  test_hash_disabled<volatile T>();
+  test_hash_disabled<const volatile T>();
 #endif
 
-    typedef std::hash<T> H;
+  typedef std::hash<T> H;
 #if TEST_STD_VER <= 17
     static_assert((std::is_same<typename H::argument_type, T>::value), "");
     static_assert((std::is_same<typename H::result_type, std::size_t>::value), "");
diff --git a/libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp b/libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp
index c798b3aa7..7fb9a953d 100644
--- a/libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp
+++ b/libcxx/test/std/utilities/function.objects/unord.hash/integral.pass.cpp
@@ -35,12 +35,12 @@ void
 test()
 {
 #if TEST_STD_VER >= 11
-    test_hash_disabled<const T>();
-    test_hash_disabled<volatile T>();
-    test_hash_disabled<const volatile T>();
+  test_hash_disabled<const T>();
+  test_hash_disabled<volatile T>();
+  test_hash_disabled<const volatile T>();
 #endif
 
-    typedef std::hash<T> H;
+  typedef std::hash<T> H;
 #if TEST_STD_VER <= 17
     static_assert((std::is_same<typename H::argument_type, T>::value), "");
     static_assert((std::is_same<typename H::result_type, std::size_t>::value), "");

ldionne

LGTM, thanks for the fix!

philnik777 · 2025-08-29T16:14:01Z

/cherry-pick 8a65c4f

llvmbot · 2025-08-29T16:20:04Z

/pull-request #156054

…55786) llvm#140407 accidentally enabled `hash` for cv-qualified types. This patch disables these specializations again. (cherry picked from commit 8a65c4f)

philnik777 requested a review from a team as a code owner August 28, 2025 08:38

llvmbot added the libc++ libc++ C++ Standard Library. Not GNU libstdc++. Not libc++abi. label Aug 28, 2025

philnik777 mentioned this pull request Aug 28, 2025

[libc++] Simplify the implementation of std::hash #140407

Merged

philnik777 changed the title ~~[libc++] Disabled cv-qualified arithmetic hash specializations~~ [libc++] Disable cv-qualified arithmetic hash specializations Aug 28, 2025

philnik777 added this to the LLVM 21.x Release milestone Aug 28, 2025

github-project-automation bot added this to LLVM Release Status Aug 28, 2025

github-project-automation bot moved this to Needs Triage in LLVM Release Status Aug 28, 2025

philnik777 force-pushed the disable_qualified_hashes branch from 88f028b to a8083ac Compare August 28, 2025 11:42

ldionne approved these changes Aug 28, 2025

View reviewed changes

github-project-automation bot moved this from Needs Triage to Needs Merge in LLVM Release Status Aug 28, 2025

[libc++] Disabled cv-qualified arithmetic hash specializations

565cf2a

philnik777 force-pushed the disable_qualified_hashes branch from a8083ac to 565cf2a Compare August 29, 2025 08:29

philnik777 merged commit 8a65c4f into llvm:main Aug 29, 2025
70 of 74 checks passed

github-project-automation bot moved this from Needs Merge to Done in LLVM Release Status Aug 29, 2025

philnik777 deleted the disable_qualified_hashes branch August 29, 2025 16:13

dwblaikie mentioned this pull request Sep 16, 2025

port 5b4819e to release #159209

Open

jhuber6 mentioned this pull request Sep 17, 2025

[LLVM] Update CUDA ELF flags for their new ABI #159451

Merged

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